Taiyi Jiuku Tianzun appears in the later chapters of Journey to the West as the lord of the East-Pole Wondrous Rock Palace. His mount is a nine-headed lion of immense cultivation, known in the mortal world as the Nine-Spirit Lion. The beast escapes when its keeper drinks the Reincarnation Jade Nectar and falls asleep for three days.
After the lion establishes itself at Bamboo-Joint Mountain and captures members of the pilgrimage party, local deities tell Sun Wukong that only its true master can subdue it. Wukong travels to the eastern celestial palace, where Taiyi questions the negligent keeper and learns how long the mount has been missing.
Taiyi then descends with Wukong and the keeper. The Nine-Spirit Lion immediately recognizes its master and is taken back under control. Taiyi explains that the lion is a long-cultivated spiritual creature whose cry can reach the three sages above and the nine springs below, yet which does not ordinarily delight in killing. His authority over this otherwise overwhelming demon is the decisive fact of the episode.